A cassette of the type with which the present invention is concerned usually includes a window within the casing so that one may perceive how much tape is on one or the other of the tape spools and hence obtain an approximate indication of the commencement position of a selected passage that is recorded on the tape. However, when a large number of separate passages are recorded on the tape, with each passage occupying only a small portion of the length of the tape, it is difficult to locate the commencement of any one passage by simply viewing the tape through the window.
Spindle driven counters of the type used in most reel-to-reel tape recorders may be, and frequently are, employed in conjunction with cassette recorders, but such counter arrangements relate to the spindle revolutions and hence relate in an indirect way only to the tape position relative to one of the spools. This means that, if a first cassette is removed from a recorder before the tape has been completely transported from one spool to the other and the recorder is subsequently used with other cassettes, when the first cassette is returned to the recorder it is most unlikely that a true indication will be given, by the counter, as to the position of the tape in the returned cassette. Then, to enable location of a desired position on the tape, the tape must be wound back to its starting position and the counter must be set to zero. Similarly, if a cassette is removed from a recorder before one "side" is completely played out and the cassette is inverted and reinserted in the recorder for the purpose of playing the second "side", then the count shown by the spindle driven counter will be inappropriate to the second side and, to enable location of a particular passage on the second side, the tape would have to be wound back to its starting position and the counter be set to zero. This may be found to be inconvenient in certain circumstances and, in any case, it is thought that it is desirable to provide means within the cassette itself for giving indication as to the position of the tape relative to the spools.